The following invention relates to a system for liberating metal in processed granulated material that may contain metal parts, such as wire, in a granulated stream of ground-up metallic and nonmetallic components, such as steel belted rubber tires.
Tires are recycled by grinding and shredding the tires to form a granular stream of material. Size reduction machines grind whole tires while downstream devices called “granulators” further reduce particle sizes. Radial tires however, and in particular steel-belted radial tires, contain wire embedded in the rubber. In order to reclaim the wire and rubber in the granulated tires separately, it is necessary to first remove the wire from the rubber in the granulated stream.
Reclaiming rubber and metal wire is a difficult process because even separated chunks of wire and rubber tend to clump together forming interwoven mats, small “birds' nests,” and other matrices of wire/rubber material. The rubber and steel mixture discharged from a granulator has been found to be at least 90% separated so that it should be feasible to reclaim the rubber and the wire correspondingly.
Conventionally, tire processors attempt to use cross-belt magnets to pick wire from a stream of material downstream from the output of a granulator. A conventional type of cross-belt magnetic separator is shown in U.S. Pat. No. 5,230,917 to Peters entitled “Method for Separation of Canned Goods and Reclaiming Useful Food Values Therefrom.” A different type of magnetic separator is shown in U.S. Pat. No. 4,055,489, Soley, “Magnetic Separator for Solid Waste.” Cross-belt magnets that attempt to separate wire from rubber are positioned at a 90° angle to a fluidized wire/rubber stream and attempt to pick the wire out of the stream. However, the mostly fluidized stream of granulated wire and rubber material that enters the magnetic field of the cross-belt magnet frequently becomes magnetized, forming a woven wire matrix with entrapped rubber. In addition to becoming magnetized, the previously separate materials change direction (i.e., make a 90° turn) as they are pulled to the corner of the magnet and are impacted by large cleats commonly found in the conveyor belts that pull the material across the cross-belt magnet. All these factors contribute to the formation of clumps of metallic and nonmetallic material mixed together.